The present invention relates to a method of installing a tubular undersea pipeline and to the corresponding undersea installation, making it possible to transport hydrocarbons between a seabed and a surface.
The exploitation of undersea oil fields requires specific installations, which are relatively complex to implement. What is particular to the marine environment is that it has a bottom covered by a greater or lesser height of water delimited by a surface and that it is not possible to maneuver freely therein. In addition, it is generally necessary to use controlled robots to install the various elements of the installations between the bottom and the surface.
These installations usually comprise a flexible or else rigid tubular undersea pipeline and a float designed to float in the vicinity of said surface in order to maintain the pipeline in suspension in the water via a coupling device. The undersea pipeline has a rising part, which extends from the seabed up to a position close to the surface below a relatively agitated region; a connecting part which makes it possible to connect the rising pipeline to surface installations designed to store a hydrocarbon; and an intermediate portion curved in a swan's neck between the substantially vertical rising part and the connecting part which extends in the form of a catenary up to the surface. The coupling device additionally makes it possible to couple together said rising part and said connecting part in suspension and to maintain said intermediate portion curved in a swan's neck between said rising part and said connecting part. Said curved intermediate portion is generally rigid and is thus generally installed in a reception frame. Reference may be made in particular to document FR 2 809 136, which describes such an installation.
This type of installation must be at least partly installed beneath the surface and in particular below the agitated region. This is because it is impossible for the tubular pipeline equipped with the coupling device to be unwound from a surface vessel and through its working well, since it is much too bulky. Thus, the rising part is first of all unwound and then maintained in suspension in the water; then the coupling device is coupled thereto in order to connect the buoy and the rising pipeline, after which the connecting part is attached by guiding it from the surface. These operations are relatively long and therefore the installation costs are high.
A problem which is then posed and which the present invention aims to solve is to provide a more economic installation method which makes it possible to install the pipeline more rapidly and with the customary means.